Automatic variable pitch propeller



Feb. 24, 1970 A. PHILLIPS 3,497,306

AUTOMATIC VARIABLE PITCH PROPELLER Filed July 11. 1968 ADRIAN PHILLIPS i aflD- Agent INVENTOR.

United States Patent 3,497,306 AUTOMATIC VARIABLE PITCH PROPELLER Adrian Phillips, 14 Deer Park Crescent, Toronto, Ontario, Canada Filed July 11, 1968, Ser. No. 744,208 Int. Cl. B63h 3/00 US. Cl. 416-136 5 Claims ABSTRACT OF THE DISCLOSURE A propeller having a hub and tail cone both secured to a drive shaft for rotation therewith. A number of blades are circumferentially spaced and project radially from the hub. Each blade has an axle which projects into and is rotatably held within a cavity in the hub. A pin is eccentrically mounted to the axle of each blade. Each pin is connected to a single load ring which is positioned about and movable along the drive shaft. A number of resilient rings are also positioned about the drive shaft within the tail cone. The rings rotate with the drive shaft and are secured between a nut and a load ring. The rings are adapted to exert a non-linear force on each pin counter to the force exerted by the fluid medium on each blade.

The present invention relates to propellers and, more particularly, to variable pitch propellers operating in a fluid medium.

To obtain optimum performance from a marine engine installation, the propeller pitch must be such that all power available at any particular power setting can be converted into effective propulsive thrust.

The three primary goals within the performance spectrum of a marine propeller may be classified as follows:

(1) Optimum economy (2) Optimum speed (3) Optimum thrust.

(a) Engine rpm. (power) (b) Boat speed (c) Propeller thrust.

These may be graphically illustrated to show their interrelationship as follows:

vg -r teal THRDS'I' QQMPOINE NT T's-em. macs? QaMFo EN BLADE blrtze'nnli 0F Q 'TA'TIQIJ 3,497,306 Patented Feb. 24, 1970 This graphic illustration may be further analyzed as follows:

T is a function of (EpAV and Q is a linear function of a. For all practical purposes in a particular blade installation both the density p and the area A may be considered as being a constant K. Then T becomes a function of LKV,

It may be seen from the above that the value of V, depends upon both the rotational velocity of the blade (V), (a function of r.p.m.), and the forward speed of the boat. Also, the horizontal component of the Thrust T must be slightly less than the torque of the engine at the selected rpm. in order that the latter can overcome the load imposed on the blade by the action of the water. Further, as the drag on the hull of a displacement hull by the action of the water increases approximately as the cube of the forward speed, a number of variables must be considered.

A typical relationship of power available to power required to propel a vessel is shown as follows:

' L POWER To effectively utilize power p at a constant r.p.m. r the pitch angle of the blades would have to be increased, resulting in an increase in angle a and coeflicient Q. The vessel, as a result, would either increase speed or become capable of pulling a greater load at the same forward speed. Under normal conditions, the speed of the vessel would increase, causing V to increase, adding to the total thrust generated by the blades. To remain at a constant r.p.m. r and fully utilize power p, it is essential that the cumulative increase in thrust brought about by the increase in pitch angle and the resultant increase in V does not exceed the amount of torque available to turn the propeller at the selected r.p.m. This torque, therefore, would have to be sufficient in magnitude to overcome the horizontal component of the total thrust so generated.

A selected increase in r.p.m., however (by using the throttle) would cause an automatic increase in V due to the increase in the rotational velocity (V) of the blades. This would cause the thrust to increase by an amount equal to the square of the increase in V,. Assuming that maximum torque was being utilized at the lower power setting, the only way in which the selected higher r.p.m. could be obtained and maintained would be by a reduction in the pitch angle which would reduce the magnitude of the horizontal component of the Thrust T, while simultaneously reducing the angle a and the coefficient (E. By this means the magnitude of the horizontal component of the Thrust T could be maintained in an amount approximately equal to the torque available. Even though the magnitude of the horizontal component of Thrust T would not be increased with an increase of r.p.m. (power), the vertical component (which propels the vessel) would increase due to the decrease in the pitch angle.

As the r.p.m. (power) is increased to a maximum, the pitch angle would have to be progressively reduced. At top speed of the vessel, the pitch angle would be at a setting between maximum and minimum, the actual position depending upon the type of vessel, speed, load end etc. Maximum thrust, i.e. propulsive thrust propelling the vessel (vertical thrust component), would be achieved when the forward speed of the vessel is at a minimum and the blades 'are in their minimum pitch angle position turning at maximum r.p.m. The selection of this minimum pitch angle position would depend upon the torque available, blade area, blade diameter, r.p.m. available and etc. so that the most desirable value of could be obtained.

Variable pitch marine propellers are known in which the blade pitch varies automatically according to changes in operating conditions. The pitch of the known blades vary linearly with changes in torque and in load on the propeller blades. Such propellers however fail to convert all the power available at any selected r.p.m. to be converted into propulsive thrust.

It is accordingly an object of this invention to provide a propeller which automatically varies the pitch of the blade in response to changes in thrust exerted by the fluid medium so that substantially all of the power available at any selected r.p.m. may be converted into propulsive thrust.

It is a further object of the invention that the blade must be increasingly restrained from rotating about the longitudinal axis in a non-linear manner as the thrust reaction on the blades increases to a maximum at the maximum r.p.m., minimums pitch angle condition.

These and other objects may be accomplished by providing means for automatically adjusting the pitch angle of the blades of a variable pitch propeller comprising the steps of rotating each blade about a longitudinal pitch axis located bet-ween the centre of pressure of the blades and the leading edges thereof by the moment of thrust of the fluid medium thereon against a non-linear resilient coupling force of variable magnitude.

In an alternate aspect of the invention, an automatic variable pitch propeller is provided for propelling a craft through a fluid medium comprising: a hub; circumferentially spaced radially projecting blades each having an axle projecting into and rotatably held within a cavity in the hub; a pin eccentn'cally mounted to the axle of each blade; and resilient means anchored at one end within the hub and adapted to exert a non-linear force on each pin counter to the force exerted by the fluid medium on each blade.

A preferred embodiment of the invention will now be described with reference to the following drawings in which like references refer to like parts thereof throughout the various views.

In the drawings:

FIGURE 1 is an elevation partly in section of one embodiment;

FIGURE 2 is a top plan view of this embodiment partly in section; and

FIGURE 3 is a section taken along the axis 3-3 of FIGURE 2.

In the drawings, the invention is shown incorporated in housing 10, hub indicated generally 12, tail cone indicated generally 14 and circumferentially spaced radially projecting blades generally indicated 44 forming a part of propeller 46. A drive shaft 16 is mounted within housing 10 and is connected to an engine by suitable means within housing 10.

As shown in FIGURE 2, propeller hub 12 is mounted on drive shaft 16 and is keyed thereto by spline 18. Hub 12 is composed of two parts 20 and 22, parts 20 and 22 being joined together by bolts 24 (shown in FIG- URE 3).

As shown in FIGURE 1, the end of drive shaft 16 is threaded, the threads thereof engaging the internal threads of anchoring cap 26, cap 26 being tubular in shape having a sealed end which encloses the end of drive shaft 16.

The exterior surface of anchoring cap 26 is threaded at its end portion 28 and is en-gageable with tightening nut 30 and lock nut 32. A plurality of resilient rings 34 are positioned about anchoring cap 26 at its intermediate portion 36. Resilient rings 34 are separated from one another by separator discs 38 and prevented from sliding off the end of anchoring cap 26 by tightening nut 30. Load ring 40 is also positioned about anchoring cap 26 and is adjacent the resilient ring 34 furthest from tightening nut 30. Resilient rings 34 are so adapted that a compressive force exerted thereon produces a non-linear amount of compression. Adjustment of resilient rings 34 can be effected by adjustment of tightening nut 30.

Tail cone 14 is secured to anchoring cap 26 by screw 24. Mounted on the periphery of hub 12 are a series of blades 44 each having an axle 48. As best seen in FIG- URE 2, each axle 48 projects into a cavity 50 in hub 12 and is rotatably held therein by a split ring 52. Each blade 44 is rotatable about a longitudinal pitch axis 33 passing through the axis of axle 48.

A pin indicated 54 is secured to each axle 48. As shown in FIGURE 3, each pin 54 is offset from axis 3-3 (i.e. is ahead of longitudinal pitch axis 33) and is engageable with load ring 40 by means of intermediary rod 56 (FIGURE 2). The position of pin '54 is such that a force from resilient rings 34 transmitted thereto by load ring 40 and intermediary rod 56 will cause blade 44 to rotate about axis 3-3 to increase the pitch angle of blade 44. Preferably each pin 54 is permanently secured to intermediary rod 56 and all intermediary rods 56 are permanently secured to load ring 40 to form one continuous interconnected body.

In operation, when propeller 46 is stationary, blade 44 is in a coarse pitch position, i.e. the pitch angle is a maximum. Blade 44 holds this position as a result of the force exerted by the resilient rings 34 and transmitted to pin 54 of propeller 46- by load ring 40 and intermediary rod 56. As propeller 46 begins to rotate the force of the fluid medium acting against centre of pressure 58 cp. (aft of longitudinal pitch axis 33) causes a couple to be set up in opposition to the force applied to pin 54 which rotates blade 44 about axis 33 against the action of resilient rings 34 to decrease the pitch angle of blade 44. As the force increases (brought about by the combination of increase in r.p.m., power, speed, etc.), the increasing moment about axis 3-3 will increasingly overbalance the force exerted by resilient rings 34 and the pitch angle of blade 44 will decrease nonlinearly to reach a point of equilibrium. If the action of the fluid medium on blades 44 is less than the force exerted by resilient rings 34, then blades 44 rotate about pitch axis 33 to a coarser pitch angle until a position of equilibrium is reached. Thus, the pitch angle adjusts continuously and automatically but non-linearly to variations in the force exerted upon the propeller. Adjustment of resilient rings 34 may be made by adjustment of tightening nut 30. Lock nut 32 secures tightening nut 30 at the desired position.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. An automatic variable pitch marine propeller for propelling a Water craft through a liquid medium comprising: a hub; circumferentially spaced radially projecting blades each having an axle projecting into and held within a cavity in said hub for notation about the blade longitudinal pitch axis, and each blade having a center of pressure aft of the said longitudinal pitch axis; connecting means eccentrically mounted on the axle of each said blade ahead of the said longitudinal pitch axis; and resilient means having non-linear force generating characteristics disposed within said hub and adapted to exert a non-linear force on each said connecting means counter to the force exerted by the fluid medium on each said blade for normally biasing said blade about its longitudinal pitch axis into its maximum coarse pitch position whereby said blade proceeds from a coarse pitch to a fine pitch with an increasing force exerted by the liquid medium.

2., Apparatus in accordance with claim 1 wherein said resilient means includes a plurality of resilient rings separated by disc means positioned about a drive shaft coaxial with said hub.

3. Apparatus in accordance with claim 1 wherein said blades are mounted to rotate about a longitudinal pitch axis located between the center of pressure :of said blades and the leading edges thereof.

4. Apparatus in accordance with claim 1 wherein said axle connecting means are pins rigidly mounted on the axle for interconnecting said axles to the resilient means. i 5. Apparatus in accordance with claim 2 wherein said axle connecting means are pins rigidly mounted on the axles for interconnecting said axles to the resilient means.

References Cited UNITED STATES PATENTS 2,099,922 11/ 1937 Bellman 17 0160.5 1 3,229,772 1/1966 Miller et al. 170160.53 3,231,023 1/1966 Marshall 170-16053 X 3,321,023 5/1967 Russell et al 170-16051 3,393,748 7/1968 Barnes 170160.53 X

FOREIGN PATENTS 614,716 9/1926 France.

791,838 10/1935 France.

434,604 9/1935 Great Britain.

61,034 5/ 194-8 Netherlands.

EVERETT A. POWELL, 1a., Primary Examiner 

